Cloning into pIBV5-His (not working)

I am trying to clone my 1.5kb gene into an insect vector known as pIB-V5His but having problems over the last 6 months. I run a typical restriction digest using SpeI and SacII for my insert and vector as follows:

Many possible things could be wrong. It is best to take a systematic approach rather than trying things at random. First, some questions.

Where does the insert DNA come from? How is it purified?
What is the concentration of insert DNA and vector DNA? How is it purified?
What is the distance between the two sites on your vector backbone?
Do you heat kill the REs prior to ligation?
Why are you using so much BSA? Are you sure it is 10x rather than 100x, which is more typical?
How are you cutting out and purifying the gel band? What wavelength are you using for the gel imaging?